The proposed experiments test the feasibility of using a new electrical response extracted from the brain waves as a method for testing hearing sensitivity. This electrical response is a composite of the so-called middle latency evoked auditory potentials, brain events that appear between 8 and 80 msec after delivery of a sound stimulus. Preliminary results with adult listeners show the new phenomenon to predict behavioral thresholds at frequencies of 250 and 500 hz with an accuracy and reliability not attained by any other known method of electric response audiometry. The experimental questions raised are: 1) Is the response present in all infants and children, including those with language disorders; 2) What threshold sensitivity does it predict for each of the standard audiometric frequencies (250 Hz and up); 3) How well do these predictions agree with behavioral or other estimates of threshold, when these are available; 4) To what extent do sleep, sedation and other changes in state influence the amplitude of the response and/or the reliability of the test. A number of experiments designed to answer the above questions are proposed; some of these are pilot studies while others systemmatically explore the effects of stimulus variables (rate, intensity, frequency), subject variables (age, sex, state of consciousness) and recording variables (electrode location, amplifier band pass) upon the amplitude of the response in question.